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Spine Thickness Does Matter

So, while I still am trying to work out an optimal thickness for a pro environment knife (a good balance between weight and geometry thickness), I took a recommendation from one of the pro guys here who used my knives, and ground one slightly thicker what I normally grind.

After some cutting at home, I liked the performance. It had a solid feel and I didn't see much decrease of cutting performance over thinner knives. It would make a good line knife - no flex, solid feel and thin above the edge (right now it's under .005").

Then I ground another knife even thicker at the spine but thin at the edge, and put it through the same cutting routine - apples, carrots, potatoes and onions. I didn't cut any proteins, as the purpose of the test was for an all-around knife.

The performance difference between the two was quite noticeable. On a thicker knife, the heel and middle of the knife wedged where on a thinner it didn't.

Both knives were ground to the same thinness at the edge, and approximately same convex 2/3 up the blade. The difference in weight was pretty negligible (officially 8g, but the heavier knife has a shorter machi, which probably took off another 8g from overall weight).

So, it seems to point to one conclusion - spine thickness does matter, regardless how thin a knife above the edge is. Spine thickness affects geometry in mid-section, which in turn affects cutting ability of a knife to go through denser foods like apples.

Here as some shots of spine, heel, profile and measurements. The spine shot is a bit distorted - those are not as thick as they look, but you can see a contrast in thickness well. Also, I come to think that spine measurements on a thinner knife are similar to 260mm Mario's Carter.

Right, so it makes sense to make two different versions of the same knife. At the weight of 220g with a handle (thicker one), it will still be a pretty light knife. The thinner version will weigh about 200g or slightly less.
What I found interesting, is that you can have a negligible weight difference, but very different performance on similarly ground knives all due to spine thickness.

You have one blade going from 3.19 to 2.71 and the other 2.93 to 2.12,those grinds are not similar at all.Are you trying to compare a similar spine tapers but at different thickness,or just a thicker middle and tip spine with the same behind the edge grind.

You have one blade going from 3.19 to 2.71 and the other 2.93 to 2.12,those grinds are not similar at all.Are you trying to compare a similar spine tapers but at different thickness,or just a thicker middle and tip spine with the same behind the edge grind.

That is a conclusion I arrived after (thicker spine translated into thicker middle). I have not ground a thick knife before and was wondering how claims that spine thickness doesn't matter as long as a knife ground thin above edge (unless above edge means middle, or more precise, hollowed out middle like in Shigefusa ). The degree of convexing was similar on both knives, but that didn't seem to matter as the thicker knife wedged in it's mid section.

I already reground it and cut some vegetables with it. Definitely a difference.